Due to the fact that most fruits cannot be consumed fresh all year round, the processing of fruits into different types of food has a very long tradition. The fruit is most often processed into fruit juices, compotes, jams and other products. The chemical composition of fruits is important both from the point of view of nutrition and from the point of view of technology. Which technological procedure will be applied, which reactions can be expected during processing, what kind of product and its quality will be obtained, is most often related to the chemical composition of the raw material. This paper analyzes plum jam and rosehip jam, and primarily considers the content of vitamin C, the content of polyphenolic compounds in rosehip jam and plum jam, and parameters important for the correctness of the product (pH, dry matter, acidity, etc.).